Lens assembly and method for forming the same

ABSTRACT

A method for forming a lens assembly is provided, including: providing a mold substrate, wherein at least a recess is formed from a surface of the mold substrate; providing a transparent substrate; disposing a lens precursor material on the surface of the mold substrate or on a first surface of the transparent substrate; disposing the mold substrate on the transparent substrate such that at least a portion of the lens precursor material is filled in the recess; disposing a mask on a second surface of the transparent substrate to partially cover the transparent substrate; after the mask is disposed, irradiating a light on the second surface of the transparent substrate to transform at least a portion of the lens precursor material on the first surface of the transparent substrate into a lens; and removing the mask and the mold substrate from the transparent substrate and the lens.

CROSS REFERENCE

This Application is a Divisional of U.S. application Ser. No.13/017,445, filed on Jan. 31, 2011 now U.S. Pat. No. 8,072,685 andentitled “Lens assembly and method for forming the same”.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens assembly and method for formingthe same, and in particular relates to an island lens assembly.

2. Description of the Related Art

Electronic imaging devices are used in a wide range of applications,such as digital cameras, digital video recorders, image capture capablemobile phones and monitors. Electronic imaging devices, such as imagesensor modules, typically convert light to electrical signals using aphotodetector. Typically, an electronic imaging device includes an imagesensor chip and a lens assembly, which is used to project an object ontothe image sensor chip. Thus, the quality of the image projection of thelens assembly determines the quality of the image signal processed bythe image sensor chip. Therefore, the quality and reliability of a lensassembly is important.

Accordingly, a lens assembly having high thermal stability, reliability,and strength is desired. In addition, fabrication time and cost of themanufacturing process of the lens assembly also need to be reduced.

BRIEF SUMMARY OF THE INVENTION

According to an illustrative embodiment, a method for forming a lensassembly is provided, including: providing a mold substrate, wherein atleast a recess is formed from a surface of the mold substrate; providinga transparent substrate; disposing a lens precursor material on thesurface of the mold substrate or on a first surface of the transparentsubstrate; disposing the mold substrate on the transparent substratesuch that at least a portion of the lens precursor material is filled inthe recess; disposing a mask on a second surface of the transparentsubstrate to partially cover the transparent substrate; after the maskis disposed, irradiating a light on the second surface of thetransparent substrate to transform at least a portion of the lensprecursor material on the first surface of the transparent substrateinto a lens; and removing the mask and the mold substrate from thetransparent substrate and the lens.

According to an illustrative embodiment, a method for forming a lensassembly is provided, which includes: providing a mold substrate,wherein a plurality of recesses are formed from a surface of the moldsubstrate; providing a transparent substrate; disposing a lens precursormaterial on the surface of the mold substrate or on a first surface ofthe transparent substrate; disposing the transparent substrate on themold substrate such that at least a portion of the lens precursormaterial is filled in the recesses; disposing a mask on a second surfaceof the transparent substrate to partially cover the transparentsubstrate; after the mask is disposed, irradiating a light on the secondsurface of the transparent substrate to transform at least a portion ofthe lens precursor material on the first surface of the transparentsubstrate into lenses; removing the mask and the mold substrate from thetransparent substrate and the lenses; and dicing the transparentsubstrate along predetermined scribe lines between the lenses to form aplurality of separate lens assemblies.

According to an illustrative embodiment, a lens assembly is provided,which includes: a transparent substrate; and a plurality of separatelenses disposed on a surface of the transparent substrate, wherein asmallest distance between any two adjacent lenses of the lenses is lessthan about 900 μm.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thesubsequent detailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1A is a cross-sectional view showing the steps of forming a lensassembly known by the inventor;

FIGS. 1B and 1C are cross-sectional views showing lens assemblies knownby the inventor;

FIGS. 2A-2F are cross-sectional views showing the steps of forming alens assembly according to an embodiment of the present invention;

FIGS. 3A-3D are cross-sectional views showing lens assemblies accordingto embodiments of the present invention;

FIGS. 4A-4B are cross-sectional views showing the steps of forming alens assembly according to an embodiment of the present invention; and

FIG. 5 is top view showing a lens assembly according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

It is understood, that the following disclosure provides many differenceembodiments, or examples, for implementing different features of theinvention. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Inaddition, the present disclosure may repeat reference numbers and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.Furthermore, descriptions of a first layer “on,” or “overlying,” (andlike descriptions) a second layer include embodiments where the firstand second layers are in direct contact and those where one or morelayers are interposing the first and second layers.

FIG. 1A is a cross-sectional view showing the steps of forming a lensassembly known by the inventor. A mold substrate is provided, whichincludes a base substrate 10 and a mold layer 12 formed thereon, whereinthe mold layer 12 is usually formed of a polymer material such as PDMS.A recess 12 a and a smaller recess 12 b adjacent to the recess 12 a areformed from a surface of the mold layer 12. A lens precursor material isdisposed on the recess 12 a. Typically, the disposed precursor materialhas a volume larger than the volume of the space in the recess 12 a. Anexcess portion of the lens precursor material may flow into the recess12 b. A substrate 100 is then placed on the mold substrate, wherein asurface 100 a of the substrate 100 faces the mold substrate and contactswith the lens precursor material filled in the recess 12 a. A light 14is irradiated from a surface 100 b of the substrate to harden the lensprecursor material. In other words, the lens precursor material filledin the recess 12 a is transformed into the lens 102. Similarly, the lensprecursor material filled in the recess 12 b is transformed into theglue buffer area 104 at least partially surrounding the lens 102.Because the recess 12 b is formed adjacent to the recess 12 a to containthe excess lens precursor material, the formed lens 102 can thereforehave a predetermined thickness and predetermined profile.

Then, the mold substrate is removed from the substrate 100 and a lensassembly is formed. FIG. 1B is a cross-sectional view showing a lensassembly obtained by the method mentioned above. As shown in FIG. 1B,the lens 102 is formed on the surface 100 a of the substrate 100. Theglue buffer area 104 is formed adjacent to the lens 102. In anothercase, when a large amount of lens precursor material is disposed on themold substrate, the obtained lens assembly may have the structure shownin FIG. 1C. As shown in FIG. 1C, a base layer 106 is formed between thelens 102 and the substrate 100.

However, the lens assemblies shown in FIGS. 1B and 1C may be deficient.For the lens assembly shown in FIG. 1B, the pitches between the adjacentlenses 102 can not be reduced due to the constraint of the glue bufferarea 104. In addition, the glue buffer area 104 may cause resistance forthermal cycling of the lens assembly to be weak. For the lens assemblyshown in FIG. 1C, the problem where the entire film peels off the baselayer 106 may occur. In addition, a strong stress may be induced due toshrinkage of the lens precursor material.

Therefore, a lens assembly having higher thermal stability and lessstress is desired. Further, the pitches between adjacent lenses need tobe reduced to improve lens assembly processing throughput.

FIGS. 2A-2F are cross-sectional views showing the steps of forming alens assembly according to an embodiment of the present invention.Referring to FIG. 2A, a mold substrate is provided, which include a basesubstrate 20 and a mold layer 22 formed thereon. An adhesion layer 21may be formed between the base substrate 20 and the mold layer 22. Atleast a recess 22 a is formed from a surface of the mold substrate. Alens will be formed in the recess 22 a in a following process. In oneembodiment, a recess 22 b adjacent to the recess 22 a and substantiallysurrounding the recess 22 a where a lens will be formed may beoptionally formed to enlarge the process window.

Next, a transparent substrate 200 having surfaces 200 a and 200 b isprovided, which is going to be disposed on the surface of the moldsubstrate. A lens precursor material 23 is disposed between the moldsubstrate and the surface 200 a of the transparent substrate 200. In oneembodiment, before the transparent substrate 200 is disposed, the lensprecursor material 23 is disposed on the surface of the mold substrate.Typically, the lens precursor material 23 is disposed only on the recess22 a where a lens will be formed and the amount of the precursormaterial 23 is usually more than what is actually needed for forming thelens to ensure the recess 22 a can be completely filled. It should beappreciated that embodiments of the invention are not limited thereto.For example, in another embodiment, the lens precursor material 23 isdisposed on the surface 200 a of the transparent substrate 200. Then,the mold substrate is disposed on the transparent substrate 200 suchthat the lens precursor material 23 is filled in the recess 22 a.

As shown in FIG. 2A, the transparent substrate 200 is disposed on themold substrate to directly contact the lens precursor material 23previously disposed in the recess 22 a. In on embodiment, thetransparent substrate 100 may further include an adhesion promoter layer(not shown) on the surface of the transparent substrate 100. Theadhesion promoter layer is capable of improving adhesion between thetransparent substrate 200 and the lens precursor material 23. When thetransparent substrate 200 is disposed on the mold substrate, an excessportion of the lens precursor material 23 may be forced to flow into therecess 22 b adjacent to the recess 22 a. Therefore, the process windowmay be enlarged.

Referring to FIG. 2B, a mask 26 is disposed on the surface 200 b of thetransparent substrate 200 to partially cover the transparent substrate200. In one embodiment, the mask 26 has at least an opening exposing aportion of the transparent substrate 200 and the portion of the lensprecursor material 23 (see FIG. 2A) filled in the recess 22 a.

After the mask 26 is disposed, a light 24 which is suitable forhardening the lens precursor material 23 is irradiated to the surface200 b of the transparent substrate 200. When the light 24 penetratesthrough the transparent substrate 200 and reaches the lens precursormaterial 23, the lens precursor material 23 is transformed into a lens202, as shown in FIG. 2B. Because the portion of the lens precursormaterial 23 filled in the recess 22 b is covered under the mask 26 andis not irradiated by the light 24, the lens precursor material 23 in therecess 22 b is not hardened. The lens precursor material 23 in therecess 22 b is referred to as a buffer area 204 hereinafter.

Next, the mask 26 and the mold substrate are removed from thetransparent substrate 200 and the lens 202, as shown in FIG. 2C. In oneembodiment, a plurality of lenses 202 are formed on the surface 200 a ofthe transparent substrate 200. A plurality of buffer areas 204 are alsoformed on the surface 200 a of the transparent substrate 200. Each ofthe lenses 202 is correspondingly surrounded by one of the buffer areas204. Because the buffer area 204 remains in the state of being a lensprecursor material, the buffer area 204 may be removed easily from thetransparent substrate 200. There is no hardened glue buffer arearemaining on the transparent substrate to cause the lens assembly to beformed having a weak resistance for thermal cycling.

Referring to FIG. 2D, the remaining portion of the lens precursormaterial 23 (i.e., the buffer areas 204) is removed from the transparentsubstrate 200. In one embodiment, a suitable solvent is used to removethe remaining portion of the lens precursor material (buffer areas 204).In one embodiment, the solvent used to remove the lens precursormaterial substantially does not remove or dissolve the formed lenses202. The material of the solvent may be varied according to the kind ofmaterial the lens precursor material uses.

As shown in FIG. 2D, after the remaining portion of the lens precursormaterial is removed, a lens assembly is formed. Compared with the lensassembly shown in FIG. 1B, no buffer area is formed. Thus, the thermalstability of the lens assembly according to an embodiment of the presentinvention is improved. Compared with the lens assembly shown in FIG. 1C,no base layer linking all of the lenses is formed and the formed lenses202 are separated from each other. Therefore, the problem where theentire film peels of the base layer is prevented. Reliability andstrength of the lens assembly according to an embodiment of the presentinvention is improved.

Referring to FIG. 2E, in one embodiment, at least a second lens 206 maybe optionally formed on the surface 200 b of the transparent substrate200. Processes similar to, but are not limited to, those shown in FIGS.2A-2D may be performed again to form the second lens 206 on the surface200 b of the transparent substrate 200. In one embodiment, a lightshielding layer 205 may be optionally formed to enhance performance ofthe formed lens assembly. In one embodiment, each of the second lenses206 correspondingly aligns with one of the lenses 202.

Next, the transparent substrate 200 may be optionally diced alongpredetermined scribe lines SC defined on the transparent substrate 200to form a plurality of separate lens assemblies. In one embodiment, thetransparent substrate 200 may be diced by using a dicing blade. Inanother embodiment, the transparent substrate 200 may be diced by usingan energy beam such as, but is not limited to, a laser beam, electronbeam, ion beam, plasma beam, the like, or combinations thereof. FIG. 2Fshows a cross-sectional view of one of the lens assemblies. Embodimentsof the invention are not limited to the lens assembly shown in FIG. 2F.Some variations and/or modifications may be made. FIGS. 3A-3D arecross-sectional views showing lens assemblies according to embodimentsof the present invention, wherein similar or same reference numbers areused to designate similar or same elements.

Referring to FIG. 3A, in one embodiment, a light shielding layer 208 maybe optionally formed to cover a portion of the lens 202 to enhanceoptical characteristics of the lens assembly. Similarly, in a case wherethe second lens 206 is formed on the surface 200 b of the transparentsubstrate, light shielding layers 208 a and 208 b may be optionallyformed on the transparent substrate 200 to partially cover the lenses202 and 206, as shown in FIG. 3B.

Referring to FIG. 3C, in one embodiment, a light shielding layer 208 maybe optionally formed on the transparent substrate 200 to enhance opticalcharacteristics of the lens assembly, wherein a portion of the lightshielding layer 208 is located between the lens 202 and the transparentsubstrate 200. Similarly, in the case where the second lens 206 isformed on the surface 200 b of the transparent substrate, lightshielding layers 208 a and 208 b may be optionally formed on thetransparent substrate 200 to enhance the optical characteristics of thelens assembly, as shown in FIG. 3D.

FIGS. 4A-4B are cross-sectional views showing the steps of forming alens assembly according to an embodiment of the present invention,wherein similar or same reference numbers are used to designate similaror same elements.

Referring to FIG. 4A, processes similar to those shown in FIGS. 2A-2Bare performed to form lenses 202 on the surface 200 a of the transparentsubstrate 200. The main difference therebetween is that no recess forbuffer area is formed from the surface of the mold substrate. Because amask is used, the light 24 only transforms specific portions of the lensprecursor material into the lenses 202. Therefore, even if an excessportion of the lens precursor material other than that to be transformedinto the lenses 202 flows to the surface 200 a of the transparentsubstrate 200, the excess portion of the lens precursor material willnot be hardened. There is no base layer or buffer area formed on thesurface 200 a of the transparent substrate 200. Therefore, the excessportion of the lens precursor material may be easily removed by using asuitable solvent.

After the mask 26 and the mold substrate are removed and the excessportion of the lens precursor material is removed, a lens assembly isformed, as shown in FIG. 4B. Because there is no recess for the bufferarea, the distance between adjacent recesses used for forming the lenses202 may be reduced. Therefore, the smallest distance W2 between theadjacent lenses 202 may be further reduced, compared with the distanceW1 of the lens assembly shown in FIG. 2D. In one embodiment, thesmallest distance W2 between adjacent lenses 202 is less than about 900μm. Because the smallest distance W2 between adjacent lenses 202 isfurther reduced, a distribution density of the lenses 202 on the surface200 a of the transparent substrate 200 can be significantly increased.In one embodiment, the distribution density of the lenses 202 on thesurface 200 a of the transparent substrate 200 may be increased to behigher than about 20 lenses/cm².

FIG. 5 is a top view showing a lens assembly according to an embodimentof the present invention, wherein similar reference numbers are used todesignate similar or same elements. In this case, the transparentsubstrate 200 having a shape similar to a wafer is used. The wafer-likelens assembly may then be diced into a plurality of lenses, and thelenses may be stacked on a semiconductor wafer, respectively.

By using the method disclosed in the embodiments of the invention toform a lens assembly, more lenses can be formed in a single transparentsubstrate. Fabrication time and cost are significantly reduced. Becauseno buffer area or base layer will be formed in the lens assemblyaccording to embodiments of the invention, thermal stability,reliability, and strength of the formed lens assembly are improved.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

What is claimed is:
 1. A lens assembly, comprising: a transparentsubstrate; and a plurality of separate lenses disposed on a surface ofthe transparent substrate, wherein a smallest distance between any twoadjacent lenses of the lenses is less than about 900 μm, wherein amaterial of the lenses comprises a polymer material.
 2. The lensassembly as claimed in claim 1, wherein the lenses directly contact withthe transparent substrate.
 3. The lens assembly as claimed in claim 1,further comprising a plurality of light shielding layers disposed on thetransparent substrate, wherein each of the light shielding layerspartially and correspondingly covers one of the lenses.
 4. The lensassembly as claimed in claim 1, further comprising a plurality of lightshielding layers disposed on the transparent substrate, wherein each ofthe light shielding layers is partially and correspondingly locatedbetween one of the lenses and the transparent substrate.
 5. The lensassembly as claimed in claim 1, further comprising a plurality of secondlenses disposed on a second surface of the transparent substrate.
 6. Thelens assembly as claimed in claim 5, wherein each of the second lensescorrespondingly aligns with one of the lenses.
 7. The lens assembly asclaimed in claim 5, wherein a smallest distance between any two adjacentsecond lenses of the second lenses is less than about 900 μm.
 8. Thelens assembly as claimed in claim 5, further comprising a plurality oflight shielding layers disposed on the transparent substrate, whereineach of the light shielding layers partially and correspondingly coversone of the second lenses.
 9. The lens assembly as claimed in claim 5,further comprising a plurality of light shielding layers disposed on thetransparent substrate, wherein each of the light shielding layers ispartially and correspondingly located between one of the second lensesand the transparent substrate.
 10. The lens assembly as claimed in claim5, wherein the second lenses directly contact with the transparentsubstrate.
 11. The lens assembly as claimed in claim 1, wherein adistribution density of the lenses on the surface of the transparentsubstrate is higher than about 20 lenses/cm².
 12. The lens assembly asclaimed in claim 1, wherein the material of the lenses is different fromthe material of the transparent substrate.
 13. A lens assembly,comprising: a transparent substrate; and a plurality of separate lensesdisposed on a surface of the transparent substrate, wherein a materialof the separate lenses comprises a polymer material.
 14. The lensassembly as claimed in claim 13, wherein the lenses directly contactwith the transparent substrate.
 15. The lens assembly as claimed inclaim 13, the material of the lenses is different from the material ofthe transparent substrate.